What Is A Polynya? What Is The Ecological Significance Of A Polynya?

An area of open water surrounded by sea ice is called a polynya. Polynyas support a wide variety of marine organisms.

The flukes of a narwhal in a Baffin Bay polynya.

What Is A Polynya?

Polynya is a Russian word that describes an area of open water surrounded by ice. They are found in both the Arctic and Antarctic in the coastal areas. Such features were once believed to be rare but they have been discovered in several places of the Arctic continent. The polynyas become visible from the space through the help of satellite images. However, sometimes it becomes hard to sight them due to the influence of the clouds. Polynyas vary in size with some as large as inland seas. Some also remain open for a number of years at a time while others recur on the same places, get smaller over time and eventually close. After some time, they dramatically reopen at one point in the seasonal cycle.

Formation Of A Polynya

They are formed through two distinct processes. The first is called sensible heat polynya and latent heat polynya. During the winters, the temperatures fall as far as -40Oc. When the cold air is blown over the ice, it insulates the water below from the extreme temperatures. However, in some instances, very strong winds blow from the land into the sea pushing away patches of ice from the coast and in the process creating the open water that are called polynyas. The process results into sensible heat polynyas. Latent heat polynyas are thermodynamically formed when warm water upwells from below and keeps the water above the freezing point. In essence, the process hinders the formation process of ice in the locality. The regions in which these kinds of polynyas are formed are also responsible for high ice production and possibly dense water production. The high level of production of ice leads also to much brine rejection onto the surface of waters. The salty water then sinks and possibly forms large masses of water. It is not yet known whether the polynyas of the Arctic can form dense waters that can adequately drive the thermohaline circulation.

Ecological Significance Of A Polynya

Some polynyas such as those between Canada and Greenland form in the same places every year and time. Because the animals in these regions can adapt to these conditions regularly, they have become so significant for the purpose of research. Polynyas are thought to be the places where the excessive and early production of planktonic herbivores ensures the transfer of solar energy into the food chain. In winter, the sea mammals such as walruses that do not migrate to the South remain in the regions. In spring, the absent or thin ice that remains allows sunlight to filter through as soon as the winter nights end. The solar energy which is tapped by the microalgae becomes very significant in the food chain. Polar bears are known to be able to travel several kilometers over open waters of polynya. The presence of polynyas is also important in the Arctic as they provide the grounds that are free of ice where the Penguins can feed. They are also critical for the purpose of Arctic navigation. In the 1950s when the US Submarines made the first expeditions to the North Pole, there were significant concerns about surfacing through the thick ice. However, a decade later, they successfully surfaced within the same large polynya near the North Pole.